Amid the deepening Ukraine crisis, Belarus has announced an extension of joint military exercises with Russia.

Against the background of the "escalation" of the conflict in eastern Ukraine, rulers Alexandr Lukashenko and Russian President Vladimir Putin decided to "continue to check the combat readiness of the armed forces of the Union state," the Belarusian Defense Ministry said on Sunday in the messenger service Telegram.

Russia had previously pledged to withdraw its soldiers from Belarus after the maneuvers ended as scheduled this Sunday.

In the Telegram post, the Belarusian ministry referred to an "increase in military activities" at the country's borders and the "deterioration of the situation in Donbass".

According to US estimates, Russia has deployed around 30,000 soldiers to Belarus for the maneuvers that have been ongoing since February 10. 

A massive Russian troop deployment on the Ukrainian border and the Belarusian-Russian maneuvers are fueling fears of an impending major Russian attack on Ukraine.

In the embattled east of Ukraine, violence has been increasing for days.

The Ukrainian army and the pro-Russian separatists in the conflict area recently accused each other of numerous violations of the ceasefire.

On Saturday, the separatists ordered a "general mobilization" and at the same time again called on women, children and the elderly to leave the country for Russia. 

NATO sees signs of 'full attack' on Ukraine

NATO Secretary General Jens Stoltenberg had already warned on Saturday evening that the alliance was expecting a comprehensive offensive by the Russian army on Ukraine.

"All signs indicate that Russia is planning a full attack on Ukraine," said Stoltenberg on Saturday evening in the ARD Tagesthemen.

The United States and NATO recently warned of a “false flag” attack by Russia.

Stoltenberg said there were signs that "Russia is preparing to create a pretext for an attack on Ukraine."

The increasing ceasefire violations in eastern Ukraine, the "false accusations" of "genocide" in the Donbass and the evacuation of the areas controlled by the pro-Russian separatists are "worrying signs". 

Russia and the former Soviet republic maintain very close relations.

Both states cooperate within the framework of the Belarusian-Russian Union, primarily in the areas of defense and economic policy.

Lukashenko traveled to Moscow on Friday for consultations with Putin.

He had recently left the withdrawal date open.

"If we make a decision, we (the force) will leave within 24 hours.

If we decide to stay for a month, they stay for a month.

The armed forces will remain as long as necessary," Lukashenko said on Thursday, according to the Belta news agency.